Yipee, someone does read what I post.
Just wondered.
Sorry about that,
the 16 is correct, the 64 is also correct, just that there is 4 rows of tanks.
The heater pads are DIY ones using softboard, electical wire,(I use salvaged electric blanket wire), thermostat, some jointers, or if you know a sparkie that can weld the wires and shrinkwrap it, vinyl for covering the lot, a staplegun with stapes, and there you have it.
As this is dealing with 240 volts, it is imperative that you know what you are doing on the electrical side, or have a friend that does.
Caryl I think, has an article on these boards, as Grant has made them.
Alan 104